The aluminum/steel cladding plates have been widely used in various fields since their combined advantages of high strength from steel and corrosion resistance from aluminum and the solved problem of welding between aluminum and steel. It is too difficult to produce aluminum/steel cladding plates in conventional way because of the difference of physical and chemical properties, especially melting point and mechanical properties, and the formation of many types of intermetallic phases between aluminum and steel. At present, the rolled cladding is the most widely used method for producing aluminum/steel cladding plates. The Al alloy in aluminum/steel plates is usually ordinary 1050 Al alloy. After Al/St rolled cladding, the serious deformation of grains leads to decreasing of ductility, moreover, further processing wouldn't be achieved. Therefore, a suitable annealing process is necessary for restoring the grains. During heat treatment, at ordinary 1050 Al alloy/steel interface, lots of brittle Fe—Al compounds would appear. By alloying with Si, the interface compounds could be suppressed. However, during brazing over 600, the brittle Fe—Al compounds would also outbreak and further induce interface brittleness and cracks for both pure Al/St and Al—Si/St if the annealing process is not suitable. The above possible defects lead to the limited working window of the heat treatment and therefore lower production stability.
Because of the large difference of physical properties between steel and aluminum, especially the melting point, the aluminum alloy played the main role during the interfacial diffusion reaction when brazing above 600° C. Thus, by alloying aluminum alloy, it can be expected different microstructure and amount of intermetallic compounds at the interface region. In the studies, it indicated that the formation of interfacial compound could effectively be inhibited by alloying with Si to Al alloy. By microalloying with Er, it could change the growth kinetics of interfacial compound, alter the distribution of interfacial brittle compound, and finally affect the interfacial bonding property. The combination of these two types of microalloying elements would further improve interfacial performance of Al/steel cladding plates.
In the invention, the composition of the aluminum alloy in the aluminum/steel cladding plates is 0.055˜0.10 wt. % Er and 0.76˜0.78 wt. % Si in weight percent. By adding both Er and Si, the generation of brittle interfacial compounds can be effectively inhibited. The corresponding working window would be broadened, which means the improvement of the production stability. Therefore, by heat treatment parameter optimizing and alloy composition design on the aluminum alloy, the amount and morphology of interface phases can be adjusted to obtain the outstanding property for high temperature brazing.